If you are an Apple user, Apple released a number of updates released late in January that will fix security vulnerabilities in several platforms and services. It was reported by US-CERT on January 23rd.
The release for Mac OSX Sierra is large, at 105 GB, and fixes many holes that would allow and attacker to remotely execute malware. This is something you should fix immediately.
The IOS release fixes an issue that can let someone bypass the lock screen code, and other issues.
The updates applied to the following products. You can click on the links that follow for the Apple security page.